The present invention relates to a rapid cooling apparatus and its method capable of completely suppressing or preventing toxic substances discharged from, for example, various incinerators, melting furnaces and the like, from synthesizing dioxins secondarily.
Cooling apparatuses employed in combustion equipment for incinerators, melting furnaces and the like are used not only in waste treatments but also widely used in industries such as metal smelting facilities, pulp bleaching processes, cement plants, glass plants, ceramic plants, plants for manufacturing chemical material or products and the like.
However, toxic dioxins are re-synthesized in cooled discharged gas from the above-mentioned facilities and plants. Consequently, the atmosphere and the global environment have been deteriorated so that it has been widely advocated that improvements on the global scale are required.
For that purpose, various kinds of rapid cooling apparatuses have been developed so as to remove dioxins, which are air pollutants and toxic.
Means to decompose dioxins by burning at high temperatures, means to prevent synthesized dioxins from generating during cooling steps of hot exhaust gas discharged to the atmosphere afterward, have been known as apparatuses or methods for removing dioxins. However these apparatuses or methods require complicated structures and cannot construct effective ones at low cost.
Organic substances and the like constituting synthetic resin such as chlorine components, hydrogen components and the like are completely reacted or decomposed into elements in the form of hot exhaust gas, when the substances are combusted in combustion equipment at temperatures higher than 800xc2x0 C. In these states, toxic dioxins are decomposed into nontoxic substances, but when the exhaust gas is cooled to a dioxin re-synthesizing temperature of ca. 340xc2x0 C. an inconvenient problem that dioxins are re-synthesized around this temperature, happens.
It was already proved through experiments and officially admitted by the Japanese government that hot exhaust gas should be rapidly cooled from 800xc2x0 C. around which the exhaust gas is in a decomposed state, to below the dioxin re-synthesizing temperature of 340xc2x0 C. within 16 thousandths second in order to prevent dioxins from re-synthesizing from decomposed hot gas at a high temperature.
The present invention is carried out in view of the above-mentioned fact in order to provide a more excellent rapid cooling apparatus and a method thereof capable of preventing dioxins from re-synthesizing by modifying or developing previous inventions (Japanese patent registered Nos. 3127249 and 3125217) invented by the present inventor.
The present invention relates to a rapid cooling apparatus equipped with multistage heat exchanger tubes for passing through coolant, arranged in a rapid cooling cylindrical body for passing hot exhaust gas comprising chemical component molecules consisting of decomposed dioxins generated in various furnaces, from an inlet opening to an outlet opening of the cylindrical body. A cross-sectional area of the rapid cooling cylindrical body is gradually diminished in a passing direction of the exhaust gas. The present invention also relates to a rapid cooling method for exchanging heat between the above-mentioned hot exhaust gas and the coolant when the exhaust gas is passed at a predetermined flow velocity which is kept at an initial velocity without reducing the flow velocity by reducing the cross-sectional area of the rapid cooling cylindrical body so as to keep up with reducing exhaust gas volume caused by dropping temperature of the exhaust gas and for cooling the exhaust gas down to a desired temperature.